题干

测定电源的电动势和内电阻的实验电路和U﹣I图像如下,回答下列问题:

①如图1所示在闭合开关之前为防止电表过载而滑动变阻器的滑动头P应放在____

②现备有以下器材:

A.干电池1个           

B.滑动变阻器(0~50Ω)         

C.滑动变阻器(0~1750Ω)D.电压表(0~3V)   

E.电压表(0~15V)      F.电流表(0~0.6A)    G.电流表(0~3A)

其中滑动变阻器应选用____,电流表应选____,电压表应选____.(填字母代号)

③如图2是根据实验数据画出的U﹣I图像.由此可知这个干电池的电动势E=____V,内电阻r=____Ω.(保留两位有效数字)

上一题 下一题 0.0难度 选择题 更新时间:2016-05-13 10:47:13

答案(点此获取答案解析)

a,B,F,D,1.5,1.0

同类题2

阅读材料,回答问题

材料一:

    中国青年报社社会调查中心联合问卷网对2026名受访者进行的一项调查显示,79.0%的受访者赞同“儿童分级阅读”。

    伴随着全民阅读活动的推进,家长为孩子购买童书或陪伴孩子阅读已经成为不少文化场所一道温暖的风景,但“究竟哪些书适合我的孩子”的确令家长很苦恼。

    如果一个孩子在10岁前还没有建立起阅读的习惯,他今后恐怕不太可能再喜欢上阅读了,所以创造更多条件把最好的阅读融入最珍贵的童年至关重要。如果孩子在儿童阶段就养成阅读的习惯、爱好,那么对于孩子一生的成长都是大有裨益的;另一方面,“童书分级”有助于儿童阅读精细化。通过精细化阅读,可以使孩子通过吸收文化知识获得更快的成长速度和更广的成长空间,有效避免“书不对路”对阅读积极性的负面影响。

(摘编自吴学安《“童书分级”并非多此一举》,2017年11月1日《北京青年报》)

材料二:

家长为儿童选购书籍主要参考依据(多选)

①A:以孩子兴趣为主

②B:根据教育专家推荐

③C:购买经典图书

④D:老师推荐的图书

⑤E:购买畅销的书籍

⑥F:自己决定

⑦G:听从书店购书建议

⑧H:随意挑选

(资料来源于中国青年报社社会调查中心联合问卷网)

材料三:

    分级阅读,是按照少年儿童不同年龄段的心智发育程度为儿童提供科学的阅读计划,为不同孩子提供不同的读物,提供科学性和有针对性的阅读图书。

    如果按照心理学和儿童发展的科学来判断儿童阅读分级必要性的话,年龄越小越适用。因为儿童的身心差异太大了,特别是婴儿时期,差一个月两个月就会有明显的认知上的不同。如果不分级,容易造成阅读压力,让儿童丧失对阅读的兴趣和信心。

    从阅读实践出发,7岁以后的阅读,视儿童在6岁前阅读习惯的建立与否,阅读水平开始逐渐拉开距离。也就是从这个时期开始,很多阅读专家反对分级阅读,觉得分级会限制大部分阅读能力强的孩子。

(摘编自保冬妮《建立科学合理的儿童分级阅读》,2017年9月12日《光明日报》)

材料四:

    在电视、手机等大众媒体的影响下,现在的儿童在兴趣、语言、服装等方面的表现都与成人区别不大了。儿童之所以会有童年,重点是儿童和成人的媒介环境是不同的,他们的媒介环境应该经过筛选和过滤。儿童分级阅读就是在塑造适合孩子的媒介环境。不过,目前国内对少儿图书分级阅读还缺乏普遍的了解和认同。虽然有一些童书已经标明了“适合X岁儿童阅读”,但是,这不是全国统一的标准,也没有详细的说明,缺乏充分的实践检验。

(摘编自赵清源《分级阅读:别让“童年的消逝”成为必然》2017.11.1《中国青年报》)

同类题5

根据短文理解,选择正确答案。

    I was in my first year of college, making friends and enjoying life, but then my whole world turned upside down. I had a heart attack. It felt like someone was stabbing (刺) me in the chest with a knife over and over again.

    After three months of rest I went back to college, but then things took a turn for the worse. I was staying at my Nana's house and woke up in the middle of the night with a terrible pain in my chest. I knew I was having a heart attack again.

    I couldn't even shout for help. Luckily my grandpa was going to the toilet and heard me falling out of bed. If it wasn't for him, I probably wouldn't be here.

    The two holes in my heart were causing the problems and I needed an operation immediately to repair them. Unfortunately, the surgery didn't go well and they only managed to repair one of the holes.

    When I woke up from the operation, I had a really dry mouth and couldn't wait to have something to eat and drink. The biggest shock of all came when I was told that I needed a heart transplant and was put on the register. The doctors were stunned at how quickly heart failure came on – it usually takes years, but it took my heart less than six months to get to that stage. My whole world came crashing down, but I stayed strong. It was a choice between crying every day and getting on with my life.

    As time went on, life became even harder. I hated feeling weak all the time and needing help with everything. It got to the point where I thought I would never get a new heart. I was diagnosed with depression.

    Even though I thought that Christmas 2008 would be my last, I really enjoyed it and even had a good New Year. Everyone was crying for me when the clock struck midnight and they told me to keep fighting.

    A week later, I got a call from the doctors saying they'd found a suitable donor (捐赠人). My wish came true and thankfully the operation went well. I spent four hours in surgery where they took out my old heart and put a new one in. When I woke up I burst out crying. I had a second chance at life.